Pneumatic Tire

ABSTRACT

In a pneumatic tire, a sipe includes an edge on a leading side and an edge on a trailing side; the edge and the edge each include a chamfered portion shorter than a sipe length of the sipe; a non-chamfered region in which other chamfered portions are not present is provided at portions facing the chamfered portions of the sipe; and for all chamfered portions, including at least the chamfered portions of the sipe, formed on grooves other than main grooves, with a ground contact width being equally divided into three in the tire lateral direction, a total volume S CE  of chamfered portions provided in a center region centrally located in the tire lateral direction and each of total volumes S SH  of chamfered portions provided in shoulder regions located on either side of the center region satisfy a relationship S CE &lt;S SH .

TECHNICAL FIELD

The present technology relates to a pneumatic tire and particularlyrelates to a pneumatic tire that can provide improved steering stabilityperformance on dry road surfaces and improved steering stabilityperformance on wet road surfaces in a compatible manner by devising asipe chamfer shape.

BACKGROUND ART

In the related art, in a tread pattern of a pneumatic tire, a pluralityof sipes are formed in a rib defined by a plurality of main grooves. Byproviding such sipes, drainage properties are ensured, and steeringstability performance on wet road surfaces is exhibited. However, when alarge number of sipes are disposed in a tread portion in order toimprove the steering stability performance on wet road surfaces, therigidity of the ribs decreases, which has the disadvantage that steeringstability performance on dry road surfaces deteriorates.

Various pneumatic tires have been proposed in which sipes are formed ina tread pattern and chamfered (for example, see Japan Unexamined PatentPublication No. 2013-537134). When the sipes are formed and chamfered,edge effects may be lost depending on the shape of the chamfers, anddepending on the dimensions of the chamfers, improvement of steeringstability performance on dry road surfaces and improvement of steeringstability performance on wet road surfaces may be insufficient.

SUMMARY

The present technology provides a pneumatic tire that can provideimproved steering stability performance on dry road surfaces andimproved steering stability performance on wet road surfaces in acompatible manner by devising a sipe chamfer shape.

A pneumatic tire according to an embodiment of the present technology isa pneumatic tire, comprising:

in a tread portion, main grooves extending in a tire circumferentialdirection; and

a sipe extending in a tire lateral direction disposed in ribs defined bythe main grooves; wherein

the sipe comprises an edge on a leading side and an edge on a trailingside;

the edge on the leading side and the edge on the trailing side eachcomprise a chamfered portion shorter than a sipe length of the sipe;

a non-chamfered region in which other chamfered portions are not presentis provided at portions facing the chamfered portions of the sipe; and

for all chamfered portions, comprising at least the chamfered portionsof the sipe, formed on grooves other than the main grooves, with aground contact width being equally divided into three in the tirelateral direction, a total volume S_(CE) of chamfered portions providedin a center region centrally located in the tread portion in the tirelateral direction and each of total volumes S_(SH) of chamfered portionsprovided in shoulder regions located on either side of the center regionsatisfy a relationship S_(CE)<S_(SH).

In an embodiment of the present technology, the pneumatic tire includessipes that extend in the tire lateral direction in ribs defined by themain grooves. The chamfered portion that is shorter than the sipe lengthof the sipe is provided on each of the edge on the leading side and theedge on the trailing side of the sipe, and the non-chamfered regions inwhich other chamfered portions are not present are disposed at theportions facing the chamfered portions of the sipe. Thus, the drainageeffect can be improved with the chamfered portions, and a water film canbe effectively removed by the edge effect in the non-chamfered regions.As a result, the steering stability performance on wet road surfaces canbe greatly improved. Moreover, the chamfered portion and thenon-chamfered region are disposed alongside each other on the edge onthe leading side and the edge on the trailing side in this manner. Thus,the effect of enhancing wet performance as described above when brakingand driving can be maximally achieved. Additionally, compared to a knownchamfered sipe, the chamfered area can be minimized, so the steeringstability performance on dry road surfaces can be improved. As a result,the steering stability performance on dry road surfaces and the steeringstability performance on wet road surfaces can be improved in acompatible manner. Furthermore, for all the chamfered portions,including at least the chamfered portions of the sipes, formed ongrooves other than the main grooves, with the ground contact width beingequally divided into three in the tire lateral direction, the totalvolume S_(CE) of the chamfered portions provided in the center regioncentrally located in the tire lateral direction can be made relativelysmall to improve the steering stability performance on dry roadsurfaces, and each of the total volumes S_(SH) of the chamfered portionsprovided in the shoulder regions located on either side of the centerregion can be made relatively large to improve the steering stabilityperformance on wet road surfaces. As a result, the steering stabilityperformance on dry road surfaces and the steering stability performanceon wet road surfaces can be enhanced in a well-balanced manner.

In an embodiment of the present technology, preferably a maximum depth x(mm) of the sipe and a maximum depth y (mm) of the chamfered portionssatisfy a relationship of Formula (1); and a sipe width of the sipe isconstant in a range from an end portion located on an inner side in atire radial direction of the chamfered portion to a groove bottom of thesipe. In this way, compared to a known chamfered sipe, the chamferedarea can be minimized, so the steering stability performance on dry roadsurfaces can be improved. As a result, the steering stabilityperformance on dry road surfaces and the steering stability performanceon wet road surfaces can be improved in a compatible manner.

x×0.1≤y≤x×0.3+1.0  (1)

In an embodiment of the present technology, preferably, for the allchamfered portions, the total volume S_(CE) of the chamfered portionsprovided in the center region and each of the total volumes S_(SH) ofthe chamfered portions provided in the shoulder regions satisfy Formula(2). In this way, the steering stability performance on dry roadsurfaces and the steering stability performance on wet road surfaces canbe enhanced in a well-balanced manner. More preferably, the range isfrom 30% to 100%.

10%≤(S _(SH) −S _(CE))/S _(CE)×100%≤200%  (2)

In an embodiment of the present technology, preferably the sipe isdisposed in two or more ribs of the ribs defined by the main grooves. Inthis way, the steering stability performance on dry road surfaces andthe steering stability performance on wet road surfaces can be enhancedin a well-balanced manner.

In an embodiment of the present technology, preferably, the allchamfered portions are configured by the chamfered portion of the sipe.In this way, the steering stability performance on dry road surfaces andthe steering stability performance on wet road surfaces can be enhancedin a well-balanced manner.

In an embodiment of the present technology, preferably, for the allchamfered portions, a total projected area A_(CE) of the chamferedportions provided in the center region and each of total projected areasA_(SH) of the chamfered portions provided in the shoulder regionssatisfy a relationship A_(CE)≥A_(SH). The shoulder regions are largecontributors to noise performance. Thus, by the total projected areaA_(SH) of the chamfered portions in the shoulder regions beingrelatively small, the ground contact pressure of the shoulder regionsbeing small, and the total volume S_(SH) of the chamfered portions inthe shoulder region being large, improvements in noise performance andimprovements in steering stability performance on wet road surfaces canbe achieved in a compatible manner.

In an embodiment of the present technology, preferably, for the allchamfered portions, the total projected area A_(CE) of the chamferedportions provided in the center region and each of the total projectedareas A_(SH) of the chamfered portions provided in the shoulder regionssatisfy Formula (3). In this way, the steering stability performance ondry road surfaces, the steering stability performance on wet roadsurfaces, and noise performance can be enhanced in a well-balancedmanner. More preferably, the range is from 3% to 8%.

1%≤(A _(CE) −A _(SH))/A _(CE)×100%≤10%  (3)

In the present technology, “volume of the chamfered portions” is thevolume of the region surrounded by the groove including the chamferedportion, the profile line of the chamfered portion, and the road contactsurface of the tread portion. In other words, it is the cut-off amountof the edge portion formed by the groove wall and the road contactsurface of the tread portion by chamfering. “Projected area of thechamfered portions” is the area measured when the chamfered portion isprojected in a normal line direction of the road contact surface of thetread portion.

In the present technology, “ground contact region” is the region on thetire circumference defined by the ground contact width. The groundcontact width is the maximum linear distance in the tire axial directionof the contact surface with a flat surface when the tire is mounted on aregular rim and inflated to a regular internal pressure, and placedvertically upon a flat surface with a regular load applied thereto.“Regular rim” is a rim defined by a standard for each tire according toa system of standards that includes standards on which tires are based,and refers to a “standard rim” in the case of JATMA (Japan AutomobileTyre Manufacturers Association, Inc.), refers to a “design rim” in thecase of TRA (The Tire & Rim Association, Inc.), and refers to a“measuring rim” in the case of ETRTO (The European Tyre and RimTechnical Organisation. “Regular internal pressure” is an air pressuredefined by standards for each tire according to a system of standardsthat includes standards on which tires are based, and refers to a“maximum air pressure” in the case of JATMA, refers to the maximum valuein the table of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”in the case of TRA, and refers to the “INFLATION PRESSURE” in the caseof ETRTO. “Regular load” is a load defined by standards for each tireaccording to a system of standards that includes standards on whichtires are based, and refers to “maximum load capacity” in the case ofJATMA, refers to the maximum value in the table of “TIRE LOAD LIMITS ATVARIOUS COLD INFLATION PRESSURES” in the case of TRA, and refers to“LOAD CAPACITY” in the case of ETRTO. “Regular load” corresponds to 88%of the loads described above for a tire on a passenger vehicle.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a meridian cross-sectional view illustrating a pneumatic tireaccording to an embodiment of the present technology.

FIG. 2 is a plan view illustrating an example of a tread portion of apneumatic tire according to the embodiment of the present technology.

FIG. 3 is a perspective view illustrating a portion of a tread portionof a pneumatic tire according to an embodiment of the presenttechnology.

FIG. 4 is a plan view illustrating a portion of a tread portion of apneumatic tire according to an embodiment of the present technology.

FIG. 5 is a plan view illustrating a sipe and a chamfered portionthereon formed in the tread portion of FIG. 4.

FIG. 6 is a cross-sectional view taken along line X-X in the directionof the arrow in FIG. 4.

FIGS. 7A and 7B are cross-sectional views illustrating a modifiedexample of a sipe and chamfered portions thereon formed in the treadportion of a pneumatic tire according to an embodiment of the presenttechnology.

FIGS. 8A and 8B are cross-sectional views illustrating a modifiedexample of a sipe and chamfered portions thereon formed in the treadportion of a pneumatic tire according to an embodiment of the presenttechnology.

FIG. 9 is a plan view illustrating another modified example of a sipeand chamfered portions thereon of a pneumatic tire according to anembodiment of the present technology.

FIGS. 10A and 10B are plan views illustrating another modified exampleof a sipe and chamfered portions thereon of a pneumatic tire accordingto an embodiment of the present technology.

FIG. 11 is a cross-sectional view taken along line Y-Y in the directionof the arrow of FIG. 4.

DETAILED DESCRIPTION

Configurations of embodiments of the present technology are described indetail below with reference to the accompanying drawings. In FIGS. 1 and2, CL denotes the tire center line. In FIG. 2, E denotes the groundcontact edges, and TW denotes the ground contact width.

As illustrated in FIG. 1, a pneumatic tire according to an embodiment ofthe present technology includes an annular tread portion 1 extending inthe tire circumferential direction, a pair of sidewall portions 2, 2disposed on both sides of the tread portion 1, and a pair of beadportions 3, 3 disposed inward of the sidewall portions 2 in the tireradial direction.

A carcass layer 4 is mounted between the pair of bead portions 3, 3. Thecarcass layer 4 includes a plurality of reinforcing cords extending inthe tire radial direction and is folded back around bead cores 5disposed in each of the bead portions 3 from a tire inner side to a tireouter side. A bead filler 6 having a triangular cross-sectional shapeformed from rubber composition is disposed on the outer circumference ofthe bead core 5.

A plurality of belt layers 7 are embedded on the outer circumferentialside of the carcass layer 4 in the tread portion 1. The belt layers 7each include a plurality of reinforcing cords that are inclined withrespect to the tire circumferential direction, with the reinforcingcords of the different layers arranged in a criss-cross manner. In thebelt layers 7, the inclination angle of the reinforcing cords withrespect to the tire circumferential direction ranges from, for example,10° to 40°. Steel cords are preferably used as the reinforcing cords ofthe belt layers 7. To improve high-speed durability, at least one beltcover layer 8, formed by arranging reinforcing cords at an angle of, forexample, not greater than 5° with respect to the tire circumferentialdirection, is disposed on an outer circumferential side of the beltlayers 7. Nylon, aramid, or similar organic fiber cords are preferablyused as the reinforcing cords of the belt cover layer 8.

Note that the tire internal structure described above represents atypical example for a pneumatic tire, and the pneumatic tire is notlimited thereto.

FIG. 2 illustrates an example of a tread portion of a pneumatic tireaccording to an embodiment of the present technology. Four main grooves9 extending in the tire circumferential direction are formed in a treadportion 1. The main grooves 9 includes a pair of inner main grooves 9A,9A located on both sides of the tire center line CL and a pair of outermain grooves 9B, 9B located on the outermost side in the tire lateraldirection. Ribs 10 are defined in the tread portion 1 by the four maingrooves 9. The ribs 10 include a center rib 100A located on the tirecenter line CL, a pair of intermediate ribs 100B, 100C located outwardof the center rib 100A in the tire lateral direction, and a pair ofshoulder ribs 100D, 100E located outward of the intermediate ribs 100B,100C in the tire lateral direction.

Sipes 11 including a pair of chamfered portions 12 are formed in each ofthe center rib 100A and the intermediate ribs 100B, 100C. The sipes 11includes a sipe 110A disposed in the center rib 100A and sipes 110B,110C disposed in each of the intermediate ribs 100B, 100C. The chamferedportions 12 include a chamfered portion 120A formed on the sipe 110A, achamfered portion 120B formed on the sipe 110B, and a chamfered portion120C formed on the sipe 110C.

The sipes 110A are inclined in the same direction with respect to thetire lateral direction and are formed at intervals in the tirecircumferential direction in the center rib 100A. The sipe 110Acommunicates at both ends with the inner main grooves 9A. That is, thesipe 110A is an open sipe.

The sipes 110B are inclined in the same direction with respect to thetire lateral direction and are formed at intervals in the tirecircumferential direction in the intermediate rib 100B. One end of thesipe 110B communicates with the inner main groove 9A, and the other endcommunicates with the outer main groove 9B. That is, the sipe 110B is anopen sipe. The sipes 110C are inclined in the same direction withrespect to the tire lateral direction and are formed at intervals in thetire circumferential direction in the intermediate rib 100C. One end ofthe sipe 110C communicates with the inner main groove 9A, and the otherend communicates with the outer main groove 9B. That is, the sipe 110Cis an open sipe.

Lug grooves 200 that do not communicate with the outer main groove 9Bextend in the tire lateral direction, are inclined in the same directionwith respect to the tire lateral direction, and are formed at intervalsin the tire circumferential direction in the shoulder ribs 100D, 100E.The lug grooves 200 include lug grooves 200A formed in the shoulder rib100D and lug grooves 200B formed in the shoulder rib 100E.

FIGS. 3 to 6 illustrate a portion of a tread portion of a pneumatic tireaccording to an embodiment of the present technology. In FIGS. 3 to 5,Tc indicates the tire circumferential direction and Tw indicates thetire lateral direction. As illustrated in FIG. 3, the ribs 10 includethe sipes 11 extending in the tire lateral direction and blocks 101defined by the sipes 11. The blocks 101 are provided side by side in thetire circumferential direction. The sipes 11 are narrow grooves having agroove width of 1.5 mm or less.

As illustrated in FIG. 4, the sipes 11 have an overall shape that iscurved and are formed in the rib 10 at intervals in the tirecircumferential direction. The sipe 11 includes an edge 11A on theleading side with respect to a rotation direction R and an edge 11B onthe trailing side with respect to the rotation direction R. Thechamfered portions 12 are formed on the edge 11A on the leading side andthe edge 11B on the trailing side.

The chamfered portions 12 includes a chamfered portion 12A on theleading side with respect to the rotation direction R and a chamferedportion 12B on the trailing side with respect to the rotation directionR. At portions facing the chamfered portions 12, non-chamfered regions13 in which other chamfered portions are not present, are provided. Inother words, a non-chamfered region 13B on the trailing side withrespect to the rotation direction R is provided at a portion facing thechamfered portion 12A, and a non-chamfered region 13A on the leadingside with respect to the rotation direction R is provided at a portionfacing the chamfered portion 12B. The chamfered portion 12 and thenon-chamfered region 13 in which other chamfered portions are notpresent, are disposed adjacent to one another on the edge 11A on theleading side and the edge 11B on the trailing side of the sipe 11 inthis manner.

As illustrated in FIG. 5, the lengths of the sipe 11 and the chamferedportions 12A, 12B in the tire lateral direction are defined as a sipelength L and chamfer lengths L_(A), L_(B), respectively. The sipe lengthL and the chamfer lengths L_(A), L_(B) are lengths in the tire lateraldirection from one end portion to the other end portion for each of thesipes 11 and the chamfered portions 12A, 12B. The chamfer lengths L_(A),L_(B) of the chamfered portions 12A, 12B are formed shorter than thesipe length L of the sipe 11.

FIG. 6 is a view orthogonal to the extension direction of the sipe 11,with the tread portion 1 cut away in the vertical direction. Asillustrated in FIG. 6, the maximum depth of the sipe 11 is x (mm) andthe maximum depth of the chamfered portion 12 is y (mm), and the sipe 11and the chamfered portion 12 are formed so that the maximum depth y (mm)is less than the maximum depth x (mm). The maximum depth x of the sipe11 is preferably from 3 mm to 8 mm.

A sipe width W of the sipe 11 is substantially constant in a range froman end portion 121 located on the inner side of the chamfered portion 12in the tire radial direction to the groove bottom of the sipe 11. In aconfiguration in which a protrusion is disposed on the groove wall ofthe sipe 11, for example, the sipe width W does not include the heightof the protrusion. Also, in a configuration in which the sipe width ofthe sipe 11 gradually narrows toward the groove bottom, the width of thesipe 11 is substantially measured as the sipe width not including thenarrow portion.

In the pneumatic tire described above, as illustrated in FIG. 2, withthe ground contact width TW being equally divided into three, the regioncentrally located in the tire lateral direction is defined as a centerregion CE, and each of the regions located on both sides of the centerregion CE is defined as a shoulder region SH. Here, for all of thechamfered portions, including at least the chamfered portions 12 of thesipes 11, formed on grooves other than the main grooves 9, a totalvolume S_(CE) of all the chamfered portions provided in the centerregion CE and each of the total volumes S_(SH) of all the chamferedportions provided in the shoulder regions SH satisfy a relationshipS_(CE)<S_(SH). In the embodiment of FIG. 2, since only the sipes 11 areprovided with chamfered portions, all of the chamfered portions formedon grooves other than the main grooves 9 (the sipes 11 and the luggrooves 200) are configured by the chamfered portions 12, and each ofthe total volumes S_(SH) of all of the chamfered portions 120B and thechamfered portions 120C provided in the shoulder regions SH is greaterthan the total volume S_(CE) of all the chamfered portions 120A, 120B,120C provided in the center region CE.

Thus, as a method for making the total volume S_(SH) of all thechamfered portions provided in the shoulder region SH greater than thetotal volume S_(CE) of all the chamfered portions provided in the centerregion CE, the total number of the sipes 11 provided in the shoulderregions SH can be made greater than the total number of the sipes 11provided in the center region CE, a chamfered portion can be provided ongrooves in addition to the sipe 11 (for example, a sipe or a lug groove)provided in the shoulder regions SH, and the like. Also, thecross-sectional shape of the chamfered portions 12 of the sipes 11provided in the center region CE and the shoulder regions SH can bevaried, and, as illustrated in FIGS. 7A and 7B, the volume of thechamfered portion 12 of the sipe 11 provided in the shoulder region SHcan be made relatively large, and, as illustrated in FIGS. 8A and 8B,the volume of the chamfered portion 12 of the sipe 11 provided in thecenter region CE can be made relatively small, such that therelationship S_(CE)<S_(SH) is satisfied.

FIGS. 7A and 7B and FIGS. 8A and 8B are diagrams illustrating modifiedexamples of sipes and chamfered portions thereon formed in the treadportion of a pneumatic tire according to an embodiment of the presenttechnology. As illustrated in FIGS. 7A and 7B, in a cross-sectional viewperpendicular to the longitudinal direction of the sipe 11, a linesegment connecting the end portions 121, 122 of the chamfered portion 12is defined as a chamfer reference line RL. Furthermore, the chamferedportion 12A and/or the chamfered portion 12B includes a profile line OLthat projects further inward in the tire radial direction than thechamfer reference line RL. A region surrounded by the profile line OL,the sipe 11, and the road contact surface of the tread portion 1 isdefined as a chamfer region Ra, and a region surrounded by the chamferreference line RL, the sipe 11, and the road contact surface is definedas a reference region Rb. In other words, the fan-shaped regionsurrounded by the two dotted lines and the profile line OL illustratedin FIGS. 7A and 7B is the chamfer region Ra, and the triangular regionsurrounded by the two dotted lines and the chamfer reference line RLillustrated in FIGS. 7A and 7B is the reference region Rb. Here, across-sectional area a of the chamfer region Ra is equal to or greaterthan a cross-sectional area b of the reference region Rb. In particular,the cross-sectional area a of the chamfer region Ra is preferablygreater than the cross-sectional area b of the reference region Rb.

As illustrated in FIGS. 8A and 8B, in a cross-sectional viewperpendicular to the longitudinal direction of the sipe 11, a linesegment connecting the end portions 121, 122 of the chamfered portion 12is defined as a chamfer reference line RL. Furthermore, the chamferedportion 12A and/or the chamfered portion 12B includes a profile line OLthat projects further outward in the tire radial direction than thechamfer reference line RL. A region surrounded by the profile line OL,the sipe 11, and the road contact surface of the tread portion 1 isdefined as a chamfer region Ra, and a region surrounded by the chamferreference line RL, the sipe 11, and the road contact surface is definedas a reference region Rb. In other words, the region surrounded by thetwo dotted lines and the profile line OL illustrated in FIGS. 8A and 8Bis the chamfer region Ra, and the triangular region surrounded by thetwo dotted lines and the chamfer reference line RL illustrated in FIGS.8A and 8B is the reference region Rb. Here, a cross-sectional area a ofthe chamfer region Ra is less than a cross-sectional area b of thereference region Rb.

In the pneumatic tire described above, the chamfered portion 12 that isshorter than the sipe length L of the sipe 11 is provided on each of theedge 11A on the leading side and the edge 11B on the trailing side ofthe sipe 11, and the non-chamfered regions 13 in which other chamferedportions are not present, are disposed at the portions facing thechamfered portions 12 of the sipe 11. Thus, the drainage effect can beimproved with the chamfered portions 12, and a water film can beeffectively removed by the edge effect in the non-chamfered regions 13in which the chamfered portion 12 is not provided. As a result, thesteering stability performance on wet road surfaces can be greatlyimproved. Moreover, the chamfered portion 12 and the non-chamferedregion 13 in which chamfered portions are not present, are disposedalongside each other on the edge 11A on the leading side and the edge11B on the trailing side in this manner. Thus, the effect of enhancingwet performance as described above when braking and driving can bemaximally achieved. Furthermore, for all the chamfered portions,including at least the chamfered portions 12 of the sipes 11, formed ongrooves other than the main grooves 9, with the ground contact width TWbeing equally divided into three in the tire lateral direction, thetotal volume S_(CE) of the chamfered portions provided in the centerregion CE centrally located in the tire lateral direction can be maderelatively small to improve the steering stability performance on dryroad surfaces, and each of the total volumes S_(SH) of the chamferedportions provided in the shoulder regions SH located on either side ofthe center region CE can be made relatively large to improve thesteering stability performance on wet road surfaces. As a result, thesteering stability performance on dry road surfaces and the steeringstability performance on wet road surfaces can be enhanced in awell-balanced manner.

In the pneumatic tire described above, the maximum depth x (mm) and themaximum depth y (mm) preferably satisfy the relationship of Formula (1)below. By providing the sipes 11 and the chamfered portions 12 so as tosatisfy the relationship of Formula (1) below, compared to a knownchamfered sipe, the chamfered area can be minimized, so the steeringstability performance on dry road surfaces can be improved. As a result,the steering stability performance on dry road surfaces and the steeringstability performance on wet road surfaces can be improved in acompatible manner. Here, when y<x×0.1 is true, the drainage effect fromthe chamfered portions 12 is insufficient, and when y>x×0.3+1.0 is true,the rigidity of the rib 10 is reduced, leading to a reduction in thesteering stability performance on dry road surfaces. In particular, therelationship y≤x×0.3+0.5 is preferably satisfied.

x×0.1≤y≤x×0.3+1.0  (1)

For all the chamfered portions described above, the total volume S_(CE)of the chamfered portions provided in the center region CE and each ofthe total volumes S_(SH) of the chamfered portions provided in theshoulder regions SH preferably satisfy the following Formula (2). Morepreferably, the range is from 30% to 100%. By appropriately setting thetotal volume difference between the total volume S_(CE) of all thechamfered portions provided in the center region CE and each of thetotal volumes S_(SH) of all the chamfered portions provided in theshoulder regions SH in this manner, both steering stability performanceon dry road surfaces and steering stability performance on wet roadsurfaces can be enhanced.

10%≤(S _(SH) −S _(CE))/S _(CE)×100%≤200%  (2)

Meanwhile, for all the chamfered portions described above, a totalprojected area A_(CE) of the chamfered portions provided in the centerregion CE and each of total projected areas A_(SH) of the chamferedportions provided in the shoulder regions SH preferably satisfy therelationship A_(CE)≥A_(SH). The shoulder regions SH are largecontributors to noise performance. Thus, by the total projected areasA_(SH) of all the chamfered portions provided in the shoulder regions SHbeing relatively small, the ground contact pressure of the shoulderregions SH being small, and the total volume S_(SH) of all the chamferedportions provided in the shoulder region SH being large, improvement innoise performance and improvement in steering stability performance onwet road surfaces can be achieved in a compatible manner.

In particular, for all the chamfered portions described above, the totalprojected area A_(CE) of the chamfered portions provided in the centerregion CE and each of the total projected areas A_(SH) of the chamferedportions provided in the shoulder regions SH preferably satisfy thefollowing Formula (3). More preferably, the range is from 3% to 8%. Byappropriately setting the total projected area A_(CE) of all thechamfered portions provided in the center region CE and the totalprojected areas A_(SH) of all the chamfered portions provided in theshoulder regions SH in this manner, the steering stability performanceon dry road surfaces, the steering stability performance on wet roadsurfaces, and noise performance can be enhanced in a well-balancedmanner.

1%≤(A _(CE) −A _(SH))/A _(CE)×100%≤10%  (3)

In the pneumatic tire described above, the sipes 11 are preferablydisposed in two or more of the ribs 10 of the plurality of ribs 10defined by the main grooves 9. With the sipes 11 being disposed in twoor more of the ribs 10 in this manner, the steering stabilityperformance on dry road surfaces and the steering stability performanceon wet road surfaces can be enhanced in a well-balanced manner.

In particular, all the chamfered portions including at least thechamfered portions 12 of the sipes 11, which are chamfered portionsformed on grooves other than the main grooves 9, are preferablyconfigured by the chamfered portion 12 of the sipe 11. In such a case, atotal volume difference (S_(SH)−S_(CE)) between the total volume S_(CE)of all the chamfered portions provided in the center region CE and thetotal volume S_(SH) of all the chamfered portions provided in theshoulder region SH is the same as a total volume difference(S_(SH)′−S_(CE)′) between a total volume S_(CE)′ of the chamferedportions 12 of the sipes 11 provided in the center region CE and a totalvolume S_(SH)′ of the chamfered portions 12 of the sipes 11 provided inthe shoulder region SH. With all of the chamfered portions describedabove being configured by the chamfered portion 12 in this manner, thesteering stability performance on dry road surfaces and the steeringstability performance on wet road surfaces can be enhanced in awell-balanced manner.

FIG. 9 is a diagram illustrating another modified example of a sipe andchamfered portions thereon formed in the tread portion of a pneumatictire according to an embodiment of the present technology. The sipe 11illustrated in FIG. 9 is formed with an inclination angle θ with respectto the tire circumferential direction. This inclination angle θ refersto the angle formed by an imaginary line (the dotted line illustrated inFIG. 9) connecting both end portions of the sipe 11 and the side surfaceof the block 101. The inclination angle θ has an inclination angle onthe acute angle side and an inclination angle on the obtuse angle side.In FIG. 9, the inclination angle θ on the acute angle side isillustrated. The inclination angle θ is the inclination angle of thesipe 11 at the intermediate pitch within the rib 10. Here, theinclination angle θ on the acute angle side is preferably from 40° to80°, and more preferably from 50° to 70°. With the sipe 11 beinginclined with respect to the tire circumferential direction in this way,pattern rigidity can be improved, and the steering stability performanceon dry road surfaces can be further improved. Here, when the inclinationangle θ is less than 40°, uneven wear resistance performance isdegraded. When the inclination angle θ exceeds 80°, pattern rigiditycannot be sufficiently improved.

In an embodiment of the present technology, the side having theinclination angle θ on the acute angle side of the sipe 11 is defined asthe acute angle side, and the side having the inclination angle θ on theobtuse angle side of the sipe 11 is defined as the obtuse angle side.The chamfered portions 12A, 12B formed on the edges 11A, 11B of the sipe11 are formed on the acute angle side of the sipe 11. With the sipe 11being chamfered on the acute angle side in this manner, uneven wearresistance performance can be further enhanced. Alternatively, thechamfered portions 12A, 12B may be formed on the obtuse angle side ofthe sipe 11. With the chamfered portion 12 being formed on the obtuseangle side of the sipe 11 in this manner, the edge effect is increased,and the steering stability performance on wet road surfaces can befurther improved.

In the present technology, the overall shape of the sipe 11 describedabove is curved, allowing the steering stability performance on wet roadsurfaces to be improved. However, a portion of the sipe 11 may have acurved or bent shape in a plan view. With the sipe 11 being formed inthis manner, the total amount of edges 11A, 11B of the sipes 11 isincreased, and the steering stability performance on wet road surfacescan be improved.

As illustrated in FIG. 9, one chamfered portion 12 is disposed on eachof the edge 11A on the leading side and the edge 11B on the trailingside of the sipe 11. By the chamfered portions 12 being disposed in thismanner, uneven wear resistance performance can be improved. Here, whentwo or more chamfered portions 12 are formed in each of the edge 11A onthe leading side and the edge 11B on the trailing side of the sipe 11,the number of nodes increases, which tends to deteriorate uneven wearresistance performance.

The maximum width of the chamfered portion 12 measured in the directionorthogonal to the sipe 11 is defined as a width W1. The maximum width W1of the chamfered portion 12 is preferably from 0.8 times to 5.0 timesthe sipe width W of the sipe 11, and more preferably from 1.2 times to3.0 times. With the maximum width W1 of the chamfered portion 12 beingappropriately set with respect to the sipe width W in this manner, thesteering stability performance on dry road surfaces and the steeringstability performance on wet road surfaces can be improved in acompatible manner. When the maximum width W1 of the chamfered portion 12is less than 0.8 times the sipe width W of the sipe 11, the steeringstability performance on wet road surfaces cannot be sufficientlyimproved, and when the maximum width W1 is greater than 5.0 times thesipe width W, the steering stability performance on dry road surfacescannot be sufficiently improved.

Furthermore, the outer edge portion in the longitudinal direction of thechamfered portion 12 is formed parallel with the extension direction ofthe sipe 11. With the chamfered portion 12 extending parallel with thesipe 11 in this way, uneven wear resistance performance can be improved,and the steering stability performance on dry road surfaces and thesteering stability performance on wet road surfaces can be improved in acompatible manner.

As illustrated in FIG. 9, end portions of the chamfered portions 12A,12B located near the main grooves 9 communicate with the main grooves 9located on either side of the rib 10. With the chamfered portions 12A,12B being formed in this manner, the steering stability performance onwet road surfaces can be further improved. Alternatively, the endportions of the chamfered portions 12A, 12B located near the maingrooves 9 may terminate within the rib 10 without communicating with themain grooves 9. With the chamfered portions 12A, 12B being formed inthis manner, the steering stability performance on dry road surfaces canbe further improved.

FIGS. 10A and 10B are diagrams illustrating another modified example ofa sipe and chamfered portions thereon formed in the tread portion of apneumatic tire according to an embodiment of the present technology. Asillustrated in FIG. 10A, the chamfered portion 12A and the chamferedportion 12B are formed so that a portion of both of the chamferedportions 12A, 12B overlap in a central portion of the sipe 11. Here, thelength in the tire lateral direction of the overlapping portion, whichis a portion where the chamfered portion 12A and the chamfered portion12B overlap, is defined as an overlap length L1. On the other hand, asillustrated in FIG. 10B, when a portion of both the chamfered portion12A and the chamfered portion 12B do not overlap and are separated by acertain interval, the proportion of the overlap length L1 with respectto the sipe length L is expressed as a negative value. The overlaplength L1 of the overlapping portion is preferably from −30% to 30% ofthe sipe length L, and more preferably from −15% to 15%. With theoverlap length L1 of the chamfered portion 12 being appropriately setwith respect to the sipe length L in this manner, the steering stabilityperformance on dry road surfaces and the steering stability performanceon wet road surfaces can be improved in a compatible manner. Here, whenthe overlap length L1 is greater than 30%, the steering stabilityperformance on dry road surfaces is not sufficiently improved, and whenthe overlap length L1 is less than −30%, the steering stabilityperformance on wet road surfaces is not sufficiently improved.

FIG. 11 is a view of the sipe cut away in the extension direction. Asillustrated in FIG. 11, the sipe 11 includes a raised bottom portion 14in a portion of the sipe 11 in the length direction. As the raisedbottom portion 14, a raised bottom portion 14A located in the centralportion of the sipe 11 and raised bottom portions 14B located at bothend portions of the sipe 11 are present. By providing the raised bottomportion 14 in the sipe 11 in this manner, the steering stabilityperformance on dry road surfaces and the steering stability performanceon wet road surfaces can be improved in a compatible manner. The raisedbottom portion 14 of the sipe 11 may be formed at the end portion and/ornot at the end portion of the sipe 11.

The height in the tire radial direction of the raised bottom portion 14formed in the sipe 11 is defined as a height H14. For the raised bottomportion 14A formed not at the end portion of the sipe 11, the maximumheight from the groove bottom of the sipe 11 to the top surface of theraised bottom portion 14A is defined as a height H_(14A). The heightH_(14A) is preferably from 0.2 times to 0.5 times the maximum depth x ofthe sipe 11, and more preferably from 0.3 times to 0.4 times. By settingthe height H_(14A) of the raised bottom portion 14A disposed not at theend portion of the sipe 11 to a suitable height, the rigidity of theblock 101 can be improved and the drainage effect can be maintained. Asa result, the steering stability performance on wet road surfaces can beimproved. Here, when the height H_(14A) is less than 0.2 times themaximum depth x of the sipe 11, the rigidity of the block 101 cannot besufficiently improved, and when the height H_(14A) is greater than 0.5times the maximum depth x of the sipe 11, the steering stabilityperformance on wet road surfaces cannot be sufficiently improved.

For the raised bottom portions 14B formed at both end portions of thesipe 11, the maximum height from the groove bottom of the sipe 11 to thetop surface of the raised bottom portion 14B is defined as a heightH_(14B). The height H_(14B) is preferably from 0.6 times to 0.9 timesthe maximum depth x of the sipe 11, and more preferably from 0.7 timesto 0.8 times. By setting the height H_(14B) of the raised bottomportions 14B disposed at the end portions of the sipe 11 to a suitableheight, the rigidity of the block 101 can be improved and the steeringstability performance on dry road surfaces can be improved. Here, whenthe height H_(14B) is less than 0.6 times the maximum depth x of thesipe 11, the rigidity of the block 101 cannot be sufficiently improved,and when the height H_(14B) is greater than 0.9 times the maximum depthx of the sipe 11, the steering stability performance on wet roadsurfaces cannot be sufficiently improved.

The length in the tire lateral direction of the raised bottom portion 14of the sipe 11 is defined as a raised bottom length L14. The raisedbottom lengths L_(14A), L_(14B) of the raised bottom portions 14A, 14Bis preferably from 0.3 times to 0.7 times the sipe length L, and morepreferably from 0.4 times to 0.6 times.

With the raised bottom lengths L_(14A), L_(14B) of the raised bottomportions 14A, 14B being appropriately set in this manner, the steeringstability performance on dry road surfaces and the steering stabilityperformance on wet road surfaces can be improved in a compatible manner.

Examples

Tires according to Conventional Examples 1, 2 and Examples 1 to 7 weremanufactured. The tires have a tire size of 245/40R19 and include, in atread portion, main grooves extending in the tire circumferentialdirection and sipes extending in the tire lateral direction disposed inribs defined by the main grooves. Also, the tires are set according toTables 1 and 2 for the following: chamfer arrangement (both sides or oneside), size relationship between sipe length L and chamfer lengthsL_(A), L_(B), chamfer provided at portion facing chamfered portion, sizerelationship between total volume S_(CE) of all chamfered portions incenter region and total volume S_(SH) of all chamfered portions inshoulder region, sipe width, total volume difference between allchamfered portions in center region and all chamfered portions inshoulder region ((S_(SH)−S_(CE))/S_(CE)×100%), number of ribs with sipesincluding chamfered portions, total volume difference between chamferedportions of sipes in center region and chamfered portions of sipes inshoulder regions ((S_(SH)′−S_(CE)′)/S_(CE)′×100%), size relationshipbetween total projected area A_(CE) of all chamfered portions in centerregion and total projected area A_(SH) of all chamfered portions inshoulder region, and total projected area difference between allchamfered portion in center region and all chamfered portions inshoulder region ((A_(CE)−A_(SH))/A_(CE)×100%).

Note that in Tables 1 and 2, when the value of the “total volumedifference between all chamfered portions in center region and allchamfered portions in shoulder region” is the same as the value of the“total volume difference between chamfered portions of sipes in centerregion and chamfered portions of sipes in shoulder region”, this meansthat all the chamfered portions including at least the chamferedportions of the sipes, which are chamfered portions formed on groovesother than main grooves, are configured by the chamfered portion of thesipe.

These test tires underwent a sensory evaluation by a test driver forsteering stability performance on dry road surfaces and steeringstability performance on wet road surfaces and a sensory evaluation fornoise performance. The results thereof are shown in Tables 1 and 2.

Sensory evaluation for steering stability performance on dry roadsurfaces and steering stability performance on wet road surfaces wasperformed with the test tires on a wheel with a rim size of 19×8.5 Jmounted on a vehicle and inflated to an air pressure of 260 kPa.Evaluation results are expressed as index values, with the results ofConventional Example 1 being assigned as an index value of 100. Largerindex values indicate superior steering stability performance on dryroad surfaces and steering stability performance on wet road surfaces.

Sensory evaluation for noise performance was performed with the testtires on a wheel with a rim size of 19×8.5 J mounted on a vehicle andinflated to an air pressure of 260 kPa. Evaluation results are expressedas index values, with the results of Conventional Example 1 beingassigned an index value of 100. Larger index values indicate superiornoise performance.

TABLE 1 Conventional Conventional Example 1 Example 2 Chamferarrangement (both sides or one side) Both sides One side Sizerelationship between sipe length L and L = L_(A), L_(B) L = L_(A)chamfer lengths L_(A), L_(B) Chamfer provided at portion facingchamfered Yes No portion Size relationship between total volume S_(CE)of all S_(CE) = S_(SH) S_(CE) = S_(SH) chamfered portions in centerregion and total volume S_(SH) of all chamfered portions in shoulderregion Sipe width Constant Changes Total volume difference between allchamfered 0% 0% portions in center region and all chamfered portions inshoulder region ((S_(SH) − S_(CE))/S_(CE) × 100%) Number of ribs withsipes including chamfered   1   1 portions Total volume differencebetween chamfered 0% 0% portions of sipes in center region and chamferedportions of sipes in shoulder region ((S_(SH)′ − S_(CE)′)/S_(CE)′ ×100%) Size relationship between total projected area A_(CE) < A_(SH)A_(CE) < A_(SH) A_(CE) of all chamfered portions in center region andtotal projected area A_(SH) of all chamfered portions in shoulder regionTotal projected area difference between all −5%  −5%  chamfered portionsin center region and all chamfered portions in shoulder region ((A_(CE)− A_(SH))/A_(CE) × 100%) Steering stability performance on dry road 100 90 surfaces Steering stability performance on wet road 100 105 surfacesNoise performance 100 100 Example 1 Example 2 Example 3 Chamferarrangement (both sides or one Both sides Both sides Both sides side)Size relationship between sipe length L L > L_(A), L_(B) L > L_(A),L_(B) L > L_(A), L_(B) and chamfer lengths L_(A), L_(B) Chamfer providedat portion facing No No No chamfered portion Size relationship betweentotal volume S_(CE) < S_(SH) S_(CE) < S_(SH) S_(CE) < S_(SH) S_(CE) ofall chamfered portions in center region and total volume S_(SH) of allchamfered portions in shoulder region Sipe width Changes ConstantConstant Total volume difference between all 5% 5% 60% chamferedportions in center region and all chamfered portions in shoulder region((S_(SH) − S_(CE))/S_(CE) × 100%) Number of ribs with sipes including  1 1  1 chamfered portions Total volume difference between 5% 5% 5%chamfered portions of sipes in center region and chamfered portions ofsipes in shoulder region ((S_(SH)′ − S_(CE)′)/S_(CE)′ × 100%) Sizerelationship between total projected A_(CE) < A_(SH) A_(CE) < A_(SH)A_(CE) < A_(SH) area A_(CE) of all chamfered portions in center regionand total projected area A_(SH) of all chamfered portions in shoulderregion Total projected area difference between −5%  −5%  −5%  allchamfered portions in center region and all chamfered portions inshoulder region ((A_(CE) − A_(SH))/A_(CE) × 100%) Steering stabilityperformance on dry 105 106 107 road surfaces Steering stabilityperformance on wet 105 106 107 road surfaces Noise performance 100 100100

TABLE 2 Example 4 Example 5 Chamfer arrangement (both sides or one side)Both sides Both sides Size relationship between sipe length L and L >L_(A), L_(B) L > L_(A), L_(B) chamfer lengths L_(A), L_(B) Chamferprovided at portion facing chamfered No No portion Size relationshipbetween total volume S_(CE) of all S_(CE) < S_(SH) S_(CE) < S_(SH)chamfered portions in center region and total volume S_(SH) of allchamfered portions in shoulder region Sipe width Constant Constant Totalvolume difference between all chamfered 60% 60% portions in centerregion and all chamfered portions in shoulder region ((S_(SH) −S_(CE))/S_(CE) × 100%) Number of ribs with sipes including chamfered  3 3 portions Total volume difference between chamfered  5% 60% portionsof sipes in center region and chamfered portions of sipes in shoulderregion ((S_(SH) ′ − S_(CE) ′)/S_(CE) ′ × 100%) Size relationship betweentotal projected area A_(CE) A_(CE) < A_(SH) A_(CE) < A_(SH) of allchamfered portions in center region and total projected area A_(SH) ofall chamfered portions in shoulder region Total projected areadifference between all −5% −5% chamfered portions in center region andall chamfered portions in shoulder region ((A_(CE) − A_(SH))/A_(CE) ×100%) Steering stability performance on dry road surfaces 108 109Steering stability performance on wet road surfaces 108 109 Noiseperformance 100 100 Example 6 Example 7 Chamfer arrangement (both sidesor one side) Both sides Both sides Size relationship between sipe lengthL and L > L_(A), L_(B) L > L_(A), L_(B) chamfer lengths L_(A), L_(B)Chamfer provided at portion facing chamfered No No portion Sizerelationship between total volume S_(CE) of all S_(CE) < S_(SH) S_(CE) <S_(SH) chamfered portions in center region and total volume S_(SH) ofall chamfered portions in shoulder region Sipe width Constant ConstantTotal volume difference between all chamfered 60% 60% portions in centerregion and all chamfered portions in shoulder region ((S_(SH) −S_(CE))/S_(CE) × 100%) Number of ribs with sipes including chamfered  3 3 portions Total volume difference between chamfered 60% 60% portionsof sipes in center region and chamfered portions of sipes in shoulderregion ((S_(SH) ′ − S_(CE) ′)/S_(CE) ′ × 100%) Size relationship betweentotal projected area A_(CE) A_(CE) = A_(SH) A_(CE) > A_(SH) of allchamfered portions in center region and total projected area A_(SH) ofall chamfered portions in shoulder region Total projected areadifference between all  0%  6% chamfered portions in center region andall chamfered portions in shoulder region ((A_(CE) − A_(SH))/A_(CE) ×100%) Steering stability performance on dry road surfaces 107 109Steering stability performance on wet road surfaces 107 109 Noiseperformance 103 105

As can be seen from Tables 1 and 2, by devising the shape of thechamfered portions formed on the sipes, the tires of Examples 1 to 7have both enhanced steering stability performance on dry road surfacesand enhanced steering stability performance on wet road surfaces.Additionally, the noise performance of the tires of Examples 6 and 7 wasalso enhanced.

1. A pneumatic tire, comprising: in a tread portion, main groovesextending in a tire circumferential direction; and a sipe extending in atire lateral direction disposed in ribs defined by the main grooves;wherein the sipe comprises an edge on a leading side and an edge on atrailing side; the edge on the leading side and the edge on the trailingside each comprise a chamfered portion shorter than a sipe length of thesipe; a non-chamfered region in which other chamfered portions are notpresent is provided at portions facing the chamfered portions of thesipe; and for all chamfered portions, comprising at least the chamferedportions of the sipe, formed on grooves other than the main grooves,with a ground contact width being equally divided into three in the tirelateral direction, a total volume S_(CE) of chamfered portions providedin a center region centrally located in the tread portion in the tirelateral direction and each of total volumes S_(SH) of chamfered portionsprovided in shoulder regions located on either side of the center regionsatisfy a relationship S_(CE)<S_(SH).
 2. The pneumatic tire according toclaim 1, wherein a maximum depth x (mm) of the sipe and a maximum depthy (mm) of the chamfered portions satisfy a relationshipx×0.1≤y≤x×0.3+1.0; and a sipe width of the sipe is constant in a rangefrom an end portion located on an inner side in a tire radial directionof the chamfered portion to a groove bottom of the sipe.
 3. Thepneumatic tire according to claim 1, wherein for the all chamferedportions, the total volume S_(CE) of the chamfered portions provided inthe center region and each of the total volumes S_(SH) of the chamferedportions provided in the shoulder regions satisfy a relationship10%≤(S_(SH)−S_(CE))/S_(CE)×100%≤200%.
 4. The pneumatic tire according toclaim 1, wherein the sipe is disposed in two or more ribs of the ribsdefined by the main grooves.
 5. The pneumatic tire according to claim 4,wherein the all chamfered portions are configured by the chamferedportion of the sipe.
 6. The pneumatic tire according to claim 1, whereinfor the all chamfered portions, a total projected area A_(CE) of thechamfered portions provided in the center region and each of totalprojected areas A_(SH) of the chamfered portions provided in theshoulder regions satisfy a relationship A_(CE)≥A_(SH).
 7. The pneumatictire according to claim 6, wherein for the all chamfered portions, thetotal projected area A_(CE) of the chamfered portions provided in thecenter region and each of the total projected areas A_(SH) of thechamfered portions provided in the shoulder regions satisfy arelationship 1%≤(A_(CE)−A_(SH))/A_(CE)×100%≤10%.
 8. The pneumatic tireaccording to claim 2, wherein for the all chamfered portions, the totalvolume S_(CE) of the chamfered portions provided in the center regionand each of the total volumes S_(SH) of the chamfered portions providedin the shoulder regions satisfy a relationship10%≤(S_(SH)−S_(CE))/S_(CE)×100%≤200%.
 9. The pneumatic tire according toclaim 8, wherein the sipe is disposed in two or more ribs of the ribsdefined by the main grooves.
 10. The pneumatic tire according to claim9, wherein the all chamfered portions are configured by the chamferedportion of the sipe.
 11. The pneumatic tire according to claim 10,wherein for the all chamfered portions, a total projected area A_(CE) ofthe chamfered portions provided in the center region and each of totalprojected areas A_(SH) of the chamfered portions provided in theshoulder regions satisfy a relationship A_(CE)≥A_(SH).
 12. The pneumatictire according to claim 11, wherein for the all chamfered portions, thetotal projected area A_(CE) of the chamfered portions provided in thecenter region and each of the total projected areas A_(SH) of thechamfered portions provided in the shoulder regions satisfy arelationship 1%≤(A_(CE)−A_(SH))/A_(CE)×100%≤10%.